ground swell noun 1.: a broad deep swell or undulation of the ocean caused by a long-continued gale or seismic disturbance and felt even at a remote distance 2.: a movement (as of political sentiment or political opinion) that is unmistakably evident but often lacking in visible leadership or overt expression < by next year the ground swell of interest among veteran and labor groups may well push cooperative housing through Congress — Catherine Bauer >